The Mangrove Periwinkle
The Mangrove Periwinkle, Littoraria angulifera (Lamarck, 1822), is an inch-long marine gastropod that inhabits the fringes of mangrove forests of the western Atlantic Ocean, including the barrier islands of Southwest Florida. Unlike its close relative, the Cloudy Periwinkle, which forms aggregations on dead tree trunks and other dead wood, the Mangrove Periwinkle prefers to live on live mangrove trees, in particular on the prop roots, trunk, and branches of Red Mangrove trees, as seen in the photo on the right. Mangrove Periwinkles browse on the film of fungi and algae that grows on the mangrove bark. Individuals of this and other periwinkle species spend all their lives out of water, except for the first couple of months of their larval life.
One of the photos (by Amy Tripp) shows a Mangrove Periwinkle, Littoraria angulifera on a red mangrove tree.